/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.dmatch;

import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.access.RowWindow;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.SlidingSizeWindowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;
import org.eclipse.collections.impl.list.mutable.primitive.DoubleArrayList;

/**
 * This function calculates DTW distance between two input series.
 */
public class UDAFDtw implements UDTF {

    private double[][] dp;
    private int m;

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(2)
                .validateInputSeriesDataType(0, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE)
                .validateInputSeriesDataType(1, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE);
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations
                .setAccessStrategy(new SlidingSizeWindowAccessStrategy(Integer.MAX_VALUE))
                .setOutputDataType(Type.DOUBLE);
    }

    @Override
    public void transform(RowWindow rowWindow, PointCollector collector) throws Exception {
        DoubleArrayList a = new DoubleArrayList();
        DoubleArrayList b = new DoubleArrayList();
        int n = rowWindow.windowSize();
        for (int i = 0; i < n; i++) {
            Row row = rowWindow.getRow(i);
            if (row.isNull(0) || row.isNull(1)) {
                continue;
            }
            a.add(Util.getValueAsDouble(row, 0));
            b.add(Util.getValueAsDouble(row, 1));
        }
        m = a.size();
        dp = new double[m + 1][m + 1];
        for (int i = 1; i <= m; i++) {
            dp[0][i] = dp[i][0] = Double.MAX_VALUE;
        }
        dp[0][0] = 0;
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= m; j++) {
                dp[i][j] =
                        Math.abs(a.get(i - 1) - b.get(j - 1))
                                + Math.min(Math.min(dp[i][j - 1], dp[i - 1][j]), dp[i - 1][j - 1]);
            }
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        collector.putDouble(0, dp[m][m]);
    }
}
